Introduction: How to Build a Simple Water Rocket

Welcome to this instructable!Whether for a school project or just for fun, building and launching your own water rocket is a challenging but awesome experience. In this tutorial we’ll show you how to get started and how to build your own, simple water rocket.

Bill of materials:

If you want, you can download a bill of material as a PDF from our Website:

Step 1: Introduction to Water Rocketry:

A water rocket is basically just a pressure vessel, filled with air and water. When you launch the rocket, the water is forced out of the vessel by the air pressure, and it accelerates the rocket in the opposite direction. But besides a bottle, which is used as the pressure vessel, you’ll need to make a safe and secure launcher too. In this case, we’ll use garden hose connectors for the launcher, because they’re water-proof and easy to release.

Step 2: The Launch Pad:

You’ll need a ½“ garden hose, which should be as long as possible. Attach a car tire valve at one end of the hose. You may have to file off a part of the valve, which will then allow you to push it into the hose. You can then secure it with a clamp. Attach the garden hose coupling at the other end of the hose. We’ll add a tap nut adaptor to the rocket later, and if we put this adaptor into the coupling we have our launcher mechanism.

If you want to have a good launcher, you’ll need a stand for your garden hose system. You can use whatever water proof materials you want for the stand, but if you want to keep it simple, just use four wooden planks like this. It’s very important that you secure the launcher to the ground so it doesn’t tip over. The stand will need to have a 16mm hole for the garden hose, and a 35mm hole for the coupling. Now you can push the hose through the small hole, and glue the coupling into the hole using a hot glue gun.

Step 3: The Nozzle:

Now it’s time to start with the construction of the nozzle, which is the adaptor between the rocket and the launch pad. Just drill a hole into a bottle cap, and increase the diameter to 14mm. Remove the seal from a 1“ tap nut adaptor, and glue the bottle cap into it using epoxy resin. Let the nozzle cure for at least 48 hours.

Step 4: Rocket and Fins:

But what about the rocket itself?You will need a stable and thick-walled plastic bottle, to make up the body of the rocket. You just have to add some fins, made of thin, stiff and lightweight wooden or plastic materials. In this case, we’re using "Guttagliss Hobbycolor". Feel free to try different fin shapes, but if you want you can download our fin templates from our website as well:

Note: For your rocket, you should use a smaller parachute than shown in this tutorial. If you prefer not to use a parachute system, that’s fine too! Just use a half tennis ball as the nosecone, and glue it in place using a hot glue gun.

Step 6: Final Steps:

After the nozzle has cured for 48 hours, you can screw it onto your rocket.

The only missing part is the release mechanism. Just attach two nylon strings to the coupling with a cable tie and divert them horizontally with a rod. The coupling’s collar will open as soon as you pull the strings.

Step 7: Launch:

Now your rocket is ready to launch. Choose a launch site, which is far away from houses, streets, trees and power lines. Secure your launcher to the ground, and attach your air pump to the hose system. Fill the rocket 1/3 full of water, and put the rocket onto your launch pad. You should raise a part of the hose above the water line in the rocket to stop water flowing back into the pump.

All you have to do now is build up the pressure with your air pump. Please be carefull, and always wear safety goggles. Don’t try to use too much pressure, 80 psi is enough for your first try. You can use more pressure later, but always be aware that the bottle can explode.

As soon as you have enough pressure, just pull the string and the rocket will launch.

We wish you much success in building your own water rocket. If you have any questions, please feel free to ask in the comments section below.

Back in the '50's, when toy manufacturing guidelines were..."looser" than today, my mom bought my brother and me pump up rockets like the ones you show. We soon discovered, as kids are wont to do, that by over-pumping (no safety valves back then) they would fly higher and faster. She really had a heart attack though when we decided to play "war" and shoot the things at each other, it had all the impact energy needed to bring down a rhino if it connected which, luckily it never did. The last we saw of them was when mom took 'em away made 'em disappear- forever.

Haha, sounds like a great childhood. ;) Our rockets have no safety valves and we launched them already at 230 PS - I don't want to know what happens if you shoot one of these rockets at another person.